xfs: implement iomap based buffered write path
Convert XFS to use the new iomap based multipage write path. This involves
implementing the ->iomap_begin and ->iomap_end methods, and switching the
buffered file write, page_mkwrite and xfs_iozero paths to the new iomap
helpers.
With this change __xfs_get_blocks will never be used for buffered writes,
and the code handling them can be removed.
Based on earlier code from Dave Chinner.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 2f37194..620fc91 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -967,3 +967,147 @@
iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
}
+
+static inline bool imap_needs_alloc(struct xfs_bmbt_irec *imap, int nimaps)
+{
+ return !nimaps ||
+ imap->br_startblock == HOLESTARTBLOCK ||
+ imap->br_startblock == DELAYSTARTBLOCK;
+}
+
+static int
+xfs_file_iomap_begin(
+ struct inode *inode,
+ loff_t offset,
+ loff_t length,
+ unsigned flags,
+ struct iomap *iomap)
+{
+ struct xfs_inode *ip = XFS_I(inode);
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_bmbt_irec imap;
+ xfs_fileoff_t offset_fsb, end_fsb;
+ int nimaps = 1, error = 0;
+
+ if (XFS_FORCED_SHUTDOWN(mp))
+ return -EIO;
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+
+ ASSERT(offset <= mp->m_super->s_maxbytes);
+ if ((xfs_fsize_t)offset + length > mp->m_super->s_maxbytes)
+ length = mp->m_super->s_maxbytes - offset;
+ offset_fsb = XFS_B_TO_FSBT(mp, offset);
+ end_fsb = XFS_B_TO_FSB(mp, offset + length);
+
+ error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+ &nimaps, XFS_BMAPI_ENTIRE);
+ if (error) {
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+ }
+
+ if ((flags & IOMAP_WRITE) && imap_needs_alloc(&imap, nimaps)) {
+ /*
+ * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
+ * pages to keep the chunks of work done where somewhat symmetric
+ * with the work writeback does. This is a completely arbitrary
+ * number pulled out of thin air as a best guess for initial
+ * testing.
+ *
+ * Note that the values needs to be less than 32-bits wide until
+ * the lower level functions are updated.
+ */
+ length = min_t(loff_t, length, 1024 * PAGE_SIZE);
+ if (xfs_get_extsz_hint(ip)) {
+ /*
+ * xfs_iomap_write_direct() expects the shared lock. It
+ * is unlocked on return.
+ */
+ xfs_ilock_demote(ip, XFS_ILOCK_EXCL);
+ error = xfs_iomap_write_direct(ip, offset, length, &imap,
+ nimaps);
+ } else {
+ error = xfs_iomap_write_delay(ip, offset, length, &imap);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ }
+
+ if (error)
+ return error;
+
+ trace_xfs_iomap_alloc(ip, offset, length, 0, &imap);
+ xfs_bmbt_to_iomap(ip, iomap, &imap);
+ } else if (nimaps) {
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ trace_xfs_iomap_found(ip, offset, length, 0, &imap);
+ xfs_bmbt_to_iomap(ip, iomap, &imap);
+ } else {
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ trace_xfs_iomap_not_found(ip, offset, length, 0, &imap);
+ iomap->blkno = IOMAP_NULL_BLOCK;
+ iomap->type = IOMAP_HOLE;
+ iomap->offset = offset;
+ iomap->length = length;
+ }
+
+ return 0;
+}
+
+static int
+xfs_file_iomap_end_delalloc(
+ struct xfs_inode *ip,
+ loff_t offset,
+ loff_t length,
+ ssize_t written)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ xfs_fileoff_t start_fsb;
+ xfs_fileoff_t end_fsb;
+ int error = 0;
+
+ start_fsb = XFS_B_TO_FSB(mp, offset + written);
+ end_fsb = XFS_B_TO_FSB(mp, offset + length);
+
+ /*
+ * Trim back delalloc blocks if we didn't manage to write the whole
+ * range reserved.
+ *
+ * We don't need to care about racing delalloc as we hold i_mutex
+ * across the reserve/allocate/unreserve calls. If there are delalloc
+ * blocks in the range, they are ours.
+ */
+ if (start_fsb < end_fsb) {
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
+ end_fsb - start_fsb);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+ if (error && !XFS_FORCED_SHUTDOWN(mp)) {
+ xfs_alert(mp, "%s: unable to clean up ino %lld",
+ __func__, ip->i_ino);
+ return error;
+ }
+ }
+
+ return 0;
+}
+
+static int
+xfs_file_iomap_end(
+ struct inode *inode,
+ loff_t offset,
+ loff_t length,
+ ssize_t written,
+ unsigned flags,
+ struct iomap *iomap)
+{
+ if ((flags & IOMAP_WRITE) && iomap->type == IOMAP_DELALLOC)
+ return xfs_file_iomap_end_delalloc(XFS_I(inode), offset,
+ length, written);
+ return 0;
+}
+
+struct iomap_ops xfs_iomap_ops = {
+ .iomap_begin = xfs_file_iomap_begin,
+ .iomap_end = xfs_file_iomap_end,
+};